Add an optimization to GlobalOpt that eliminates calls to __cxa_atexit, if the function passed is empty.

llvm-svn: 127970

1 files changed, 31 insertions, 0 deletions

diff --git a/llvm/test/Transforms/GlobalOpt/cxx-dtor.ll b/llvm/test/Transforms/GlobalOpt/cxx-dtor.ll
new file mode 100644
index 00000000000..22635620baa
--- /dev/null
+++ b/llvm/test/Transforms/GlobalOpt/cxx-dtor.ll
@@ -0,0 +1,31 @@
+; RUN: opt < %s -globalopt -S | FileCheck %s
+
+%0 = type { i32, void ()* }
+%struct.A = type { i8 }
+
+@a = global %struct.A zeroinitializer, align 1
+@__dso_handle = external global i8*
+@llvm.global_ctors = appending global [1 x %0] [%0 { i32 65535, void ()* @_GLOBAL__I_a }]
+
+; CHECK-NOT: call i32 @__cxa_atexit
+
+define internal void @__cxx_global_var_init() nounwind section "__TEXT,__StaticInit,regular,pure_instructions" {
+  %1 = call i32 @__cxa_atexit(void (i8*)* bitcast (void (%struct.A*)* @_ZN1AD1Ev to void (i8*)*), i8* getelementptr inbounds (%struct.A* @a, i32 0, i32 0), i8* bitcast (i8** @__dso_handle to i8*))
+  ret void
+}
+
+define linkonce_odr void @_ZN1AD1Ev(%struct.A* %this) nounwind align 2 {
+  call void @_ZN1AD2Ev(%struct.A* %this)
+  ret void
+}
+
+declare i32 @__cxa_atexit(void (i8*)*, i8*, i8*)
+
+define linkonce_odr void @_ZN1AD2Ev(%struct.A* %this) nounwind align 2 {
+  ret void
+}
+
+define internal void @_GLOBAL__I_a() nounwind section "__TEXT,__StaticInit,regular,pure_instructions" {
+  call void @__cxx_global_var_init()
+  ret void
+}